[netdevice] Remove const from MockEthernetImpl

llvm/llvm-project#121419 added
-Wignored-qualifiers diagnostic for cv-qualified base
classes. This patch removes const from MockEthernetImpl
to fix the -Wignored-qualifiers error.

Bug: 391704289
Change-Id: I0d5bce970d6e91febe7a5f775b35b0b2e1383245
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1192542
Commit-Queue: Auto-Submit <[email protected]>
Reviewed-by: Bruno Dal Bo <[email protected]>
Fuchsia-Auto-Submit: Gulfem Savrun Yeniceri <[email protected]>

Author: gulfemsavrun

src/connectivity/ethernet/drivers/ethernet/netdevice-migration/unit-tests.cc

@@ -251,14 +251,14 @@ class NetdeviceMigrationTest : public ::testing::Test {
   testing::StrictMock<const MockNetworkDeviceIfc>& MockNetworkDevice() {
     return mock_network_device_ifc_;
   }
-  testing::StrictMock<const MockEthernetImpl>& MockEthernet() { return mock_ethernet_impl_; }
+  testing::StrictMock<MockEthernetImpl>& MockEthernet() { return mock_ethernet_impl_; }
   netdevice_migration::NetdeviceMigration& Device() { return *device_; }
   netdevice_migration::NetdeviceMigration* TakeDevice() { return device_.release(); }
 
  private:
   const std::shared_ptr<MockDevice> parent_;
   testing::StrictMock<const MockNetworkDeviceIfc> mock_network_device_ifc_;
-  testing::StrictMock<const MockEthernetImpl> mock_ethernet_impl_;
+  testing::StrictMock<MockEthernetImpl> mock_ethernet_impl_;
   std::unique_ptr<netdevice_migration::NetdeviceMigration> device_;
   bool queued_rx_space_ = false;
 };